1. Field of Invention
This invention relates to hitches for connecting a trailer to a vehicle, and more particularly, to a method and apparatus for sliding a fifth-wheel trailer hitch head assembly.
2. Description of Related Art
Trailers are often secured to a vehicle so as to enable the vehicle to tow a load or a trailer containing recreational living quarters. Various means have been adapted for connecting the trailer to the tow vehicle including what is known in the art as a fifth-wheel trailer hitch.
In a fifth-wheel trailer hitch, the trailer includes a forwardly projecting arm which includes a vertical kingpin projecting out of a horizontal portion of the pin box. The kingpin is received within a corresponding slot of a trailer hitch plate located on the tow vehicle. The kingpin is then secured in the slot of the trailer hitch plate so as to enable the tow vehicle to tow the trailer.
The fifth-wheel trailer hitch assembly has many advantages that make it attractive for use in towing large trailers. Particularly, the engagement of a pin in a horizontal surface of the trailer hitch assembly allows the trailer hitch of a fifth-wheel hitch assembly to be located at any location on a vehicle desired by a user. Correspondingly, a ball-type trailer hitch assembly is limited to being located at the rear of a vehicle.
The ability to locate the trailer hitch assembly at any location desired by the user enables the trailer hitch of fifth-wheel hitch assembly to be located at the center of the vehicle at a point between the two rear wheels above the rear axle. Locating the trailer hitch assembly above the rear axle serves to transfer the portion of the weight of the trailer applied on the trailer arm to a position above the axles rather than at a distance from the axles as in the case of a ball joint. This serves to reduce stresses imparted to the frame and bumper of a tow vehicle. In addition the weight transferred to the rear tires of the tow vehicle is not increased by as great a degree as is the case in a ball hitch where the distance from the ball hitch to the rear axle creates a moment arm thereby increasing the weight applied to the rear tires.
A conventional fifth-wheel trailer hitch assembly, however, includes several deficiencies. When the tow vehicle is towing the trailer in a straight line, the front edge of the trailer and the rear edge of the tow vehicle will be in a parallel orientation to each other. As the tow vehicle negotiates a turn, however, the front edge of the trailer will be rotated relative to the rear edge of the tow vehicle. This will bring one corner of the trailer closer to its opposing corner of the tow vehicle. If the trailer arm connecting the trailer to the fifth-wheel hitch is not long enough, when the tow vehicle negotiates a turn, the aforementioned corner of the trailer may become quite close to or even contact its corresponding corner of the tow vehicle.
Accordingly, relatively long trailer arms are necessary to provide ample clearance between the trailer and the tow vehicle during all anticipated orientations of the trailer relative to the tow vehicle. Opposing the requirement for longer trailer arms, is the requirement to maintain efficient operation of the vehicle and trailer. In order to maintain efficient operation of the vehicle and trailer, it is desirable to maintain the distance between the trailer and the tow vehicle as low as possible so as to reduce drag and instability.
In the past, a balance has been struck when selecting the distance between the trailer and the tow vehicle so as to allow efficient operation while still enabling sufficient range of maneuverability. What is desirable is to provide a fifth-wheel hitch assembly which is able to move rearward while turning to enable ample maneuverability of the tow vehicle and trailer while being able to be subsequently moved forward to an optimal straight line tow position thereby shortening the distance between the tow vehicle and the trailer.
Various attempts have been made to provide a trailer hitch assembly that is moveable with respect to the tow vehicle so as to increase the maneuverability of the tow vehicle and trailer. For example, various attempts have been made to provide a sliding trailer hitch assembly which is lockable at a plurality of positions. In such a trailer hitch assembly, a user may unlock the sliding hitch assembly and slide it to a second position. At the second position, the vehicle and trailer may negotiate a tight turn. Thereafter, the user may unlock the sliding trailer hitch assembly from the second position and slide it back to a first position. Examples of such attempts may be shown in U.S. Pat. No. 6,357,777.
Such trailer hitch assemblies having a sliding lockable assembly are not able to automatically move the pivot point of the fifth-wheel hitch assembly rearward when the vehicle begins to negotiate a turn. Rather the entire trailer and tow vehicle must be stopped so that the user may manually reposition the hitch assembly. When the vehicle and trailer have completed the turn, the vehicle must once again be stopped so that the hitch assembly may be moved back to it's preferred straight line towing position. This is a time consuming process that a user is required to undertake before performing any turns of greater than a given radius. In addition, if the user neglects to perform these activities before negotiating the turn, the aforementioned damage of the trailer impacting the tow vehicle may still occur.
In addition, various attempts have been made to provide a pair of substantially perpendicular slots with a common body having a pivot in each of the slots. The body is connected to the trailer wherein the slots are located on a vehicle. When the trailer and thereby the body is rotated relative to the slots and the vehicle, the pivot located in a slot perpendicular to the vehicle is displaced laterally in the vehicle thereby allowing a pivot located in a slot parallel to the vehicle to be displaced longitudinally relative to the vehicle. As the trailer hitch is mounted substantially above the second pivot point, the trailer hitch will accordingly be displaced longitudinally in the vehicle as the vehicle and trailer negotiate a turn. The resulting assembly is highly dependent upon anti-friction means such as grease or bearings. Accordingly, if the assembly is not maintained properly, large angle turns negotiated by the tow vehicle may induce too large a force on the assembly and may therefore jam the assembly. Examples of such a system may be seen in U.S. Pat. No. 6,308,977.
What would be desirable is a simple way of providing a sliding fifth-wheel hitch assembly operable to automatically displace the pivot point of a trailer rearward in the tow vehicle as the tow vehicle and trailer negotiate a turn and thereafter return the pivot point back to the pre-selected straight line towing position when the trailer and tow vehicle complete the turn.